KR20170134538A - Drain valve - Google Patents

Abstract

A hydraulic system for a multiple friction transmission, comprising: a first pressure relief valve adjustable by means of a first pilot pressure; A normally-open drain valve switchable between an open state and a closed state by means of a second pilot pressure; At least one first pressure regulator for respectively actuating the directional valve and the drain valve by means of a first pilot pressure and a second pilot pressure; In the event of a harmful hydraulic pressure rise, the second pilot pressure drops to open the drain valve to release pressure through the drain line.

Description

Drain valve

The present invention relates to a hydraulic system for multiple friction transmissions comprising redundant fail safe.

Generally, a transmission provides a controlled application of engine power by switching speed and torque from a power source, such as, for example, an internal combustion engine. The hydraulic system may connect the transmission input to a geartrain to provide the actuation of friction elements in the vehicle transmission for transmitting engine power to the wheels of the vehicle. For example, a clutch module of a dual clutch transmission (DCT) typically includes two friction clutches that connect wheels to the engine via a gear train by actuation of these clutches through the hydraulic system . In the variant, three rotating members, one member being connected to the input, one member being connected to the output, and a third member being connectable to the transmission housing by means of the actuation of the friction brake, One or more clutches may be made by using a powersplit mechanism with rotational members. Multiple configurations of these friction elements (clutches, brakes) can produce various layouts of multi-friction transmissions. This type of transmission system is known, for example, from US2013184119.

The brake and / or clutch elements can generate considerable heat and the hydraulic system can also provide cooling fluid to each of the clutches and / or brakes of the transmission.

In a multiple friction transmission, such as a dual clutch transmission (DCT), for example, the dual wet clutch may be oil cooled. In general, the electrohydraulic control of a dual-clutch transmission offers significantly improved efficiency and performance while maintaining full shift comfort in traditional step automatics. Accurate and quick clutch control may be enabled by direct acting solenoids, which operate the valves electromechanically.

Essentially, the DCT can be a wet clutch or a dry clutch design. The wet clutch design is advantageously used for higher torque engines, while the dry clutch design is generally suitable for smaller torque engines. Although the dry clutch variations of the DCT can be limited in torque generation relative to their wet clutch counterparts, the dry clutch deformations can provide improved fuel efficiency primarily due to cooling and lubrication. The wet clutch requires transmission fuel pumping in the clutch housing, which results in loss. Thus, in addition, the cooling system of the multi-friction transmission can play an important role in the overall efficiency of the transmission.

The DCT layout can be independently shifted and clutched to enable uninterrupted gear shifting transmissions in the form of an automatic transmission while maintaining high mechanical efficiency over a manual transmission, Is equivalent to having two transmissions in one housing, such as one power transmission assembly, on each of two input shafts driving an output shaft together.

The pump pressure of the clutch and / or brake actuation line in the hydraulic system determines whether the clutch element and / or the brake element is actuated or not. When the operating pressure in the clutch operating line is low, the clutch is released. Normally, a normally closed (NC) solenoid valve is arranged in the clutch operating line, for example, due to a failure caused by an electrical malfunction, the first pressure circuit needs to be depressurized The valve automatically closes to prevent loss of control. However, if the valve fails at the open position, the pressure in the clutch operating line can be kept high, which is undesirable. It is desirable that this condition in which the clutch is held under pressure by avoiding that the engine can not be released is avoided. Thus, if the hydraulic pressure at the clutch and / or brake operating line is unexpectedly too high, for any reason, a loss of user control over the vehicle can be caused. In the prior art, this problem is usually addressed by providing two NC solenoid valves to the operating lines of the hydraulic circuit, one in series and one hydraulically connected behind the other. If one of the two valves fails in an open state, the other valve may still be used to control the pressure in the clutch and / or brake actuation line.

However, since the arrangement of solenoid valves including electronic components is significantly more expensive than spool valves, i.e. valves controlled by terminal fluid pressure, The technical solutions described above are generally not expensive and economically attractive. Also, spool valves are generally more robust and longer in life than solenoid valves.

The publication US2007 / 0107421A1 discloses a hydraulic circuit for an engine-driven vehicle including a high-pressure circuit and a low-pressure circuit. The hydraulic system controls fluid communication with an infinitely variable transmission (IVT) including high pressure hydraulic control devices and low pressure IVT hydraulic control clutches. When the requirements of the high pressure control devices are met, the relief valve is opened and supplies fluid from a first high pressure supply line to a second lower pressure supply line. In this manner, the low pressure pump can be minimized to supply only the usual requirements of the clutch unit. However, the pressure-build up in the friction element operating line, such as the clutch operating line and / or the brake operating line, which is connected to the high-pressure circuit, can result in a loss of control of the engine-driven vehicle.

Insufficient cooling can shorten component life and ultimately lead to failure of clutch assemblies in multi-friction transmissions. In addition, insufficient cooling can cause rapid degradation of the physical properties of the transmission fluid, which can lead to failure of other components in the multi-friction transmission.

Generally, the clutch assemblies are cooled by the transmission fluid in a generally uncontrolled manner to provide sufficient cooling for excessive heat generated in the multi-friction transmission. However, this cooling strategy generally results in a loss in efficiency by overfilling the clutch assemblies with fluid to provide sufficient heat reduction.

Also, high loading conditions can result in excessive heat generation. Conventional thermal strategies are not appropriate or not suited to effectively quench the rapid thermal rise. Thus, excessive demands are placed on the pump to provide the fluid required in these cases.

In the prior art, conventional cooling approaches of multi-friction transmissions generally use a single hydraulic cooling circuit to supply cooling fluid from the cooling device to the clutches. Cooling is controlled by the fluid pressure in the hydraulic cooling circuit to provide a flow of cooling fluid to each of the clutches of the multi-friction transmission.

Often, the DCT cooling system limits the total oil flow to both clutches when there is no hydraulic fluid or when the amount of hydraulic oil is low. Generally, the flow limiter is arranged as a differential pressure regulator that keeps the pressure drop constant for the flow regulators. This function limits the pressure of the cooling lines so that the low pressure pump can work at low pressure, thus consuming less power. Often, however, the clutches require different cooling due to differences in clutch power dissipation. At present, this is not optimally processed by cooling strategies in the prior art, and efficiency is reduced.

It can be difficult or complicated to control and adjust the hydraulic system for the multi-friction transmission to achieve the comfort and safety goals of the desired vehicle occupant. Implementation of appropriate timing and events is required for efficient and / or smooth gear shifting.

Thus, there is a need for a hydraulic system for a multiple friction transmission that handles at least one of the aforementioned drawbacks while maintaining the advantages.

To this end, the invention provides a hydraulic system for a multiple friction transmission according to claim 1.

The multi-friction transmission is configured to transmit and transmit engine power from the engine to the wheels of the vehicle by operation of a brake element and a clutch element via the hydraulic system. A brake element and a clutch element.

The hydraulic system also includes at least one pressure pump for supplying pressurized fluid to a first pressure circuit through a first pressure pump outlet line. do. The first pressure circuit is in fluid connection with the brake actuation line and the clutch actuation line, respectively operating the brake element and the clutch element. The hydraulic system further includes a first pressure relief valve arranged in a pressure controlled hydraulic line that branches off from the first pressure pump outlet line. The first pressure relief valve includes at least one first pressure regulator for activating the first pressure relief valve by means of a first pilot pressure through a first pilot pressure line, By means of the first pilot pressure through the first pilot pressure line. The hydraulic system further includes a drain valve arranged in a pressure drain hydraulic line which branches off from the first pressure pump outlet line, which is different from the pressure control hydraulic line. The drain valve is a normally-open (NO) directional valve switchable between an open state and a closed state by means of a second pilot pressure through a second pilot pressure line, the second pilot pressure line being, for example, The second pilot pressure line is branched from the first pilot pressure line. In a fail safe event, for example when the harmful hydraulic pressure builds up in the first pressure circuit, the second pilot pressure is dropped by at least one first pressure regulator and NO The drain valve is switched from the closed operating state to the open non-operating state, thereby at least partially discharging the hydraulic pressure through the drain line from the first pressure circuit, resulting in an extra passive fail safe of the hydraulic system. The fail safe provided by the drain valve avoids the use of expensive additional valves in the clutch and / or brake actuation line. Also, the first pressure relief valve may not be suitable for quickly releasing the first pressure circuit when desired, as opposed to the drain valve.

The pressure regulator is operable, for example, when an unexpected pressure rise is detected in at least one of the clutch and / or brake actuation lines connected to the first pressure circuit of the hydraulic system due to mechanical and / or electrical malfunction, 1 pilot pressure in the first and second pilot pressure lines lower than a preset value necessary for operation of the pressure relief valve. As a result, the NO drain valve will open and drain excess pressure from the first pressure circuit.

The cost of the hydraulic system of the multiple friction transmission can be reduced while eliminating the need to arrange the redundant solenoid valves one hydraulically connected behind the other in series in the clutch and / or brake actuation line. According to one aspect, a hydraulic system is obtained with a passive fail-safe valve. This hydraulic system does not require expensive technical features that can meet the problems associated with providing the fail safe. The hydraulic system will maintain the safe operation of the transmission when, for example, a pressure rise occurs in the pressure circuit connected to the clutch and / or brake actuation line due to mechanical, electronic, electrical failure of one or more components. The hydraulic system may also be used to cool the clutch and / or brakes of the transmission.

Optionally, the drain valve is a normally-open (NO) directional valve. By arranging the NO drain valve, a passive fail safe can be obtained and, for example, in the case of a detrimental pressure rise in the operating lines, in order to reduce the hydraulic pressure in at least one of the clutch and / Pressure and / or current is not required for the hydraulic system capable of draining the first pressure circuit.

Optionally, the drain valve is a normally-closed (NC) directional valve. A hydraulic system comprising an NC drain valve will require a second pilot pressure which is provided to the drain valve by a first pressure regulator through a second pilot pressure line such that at least one of the clutches and / The drain valve is opened to drain the first pressure circuit.

The hydraulic system may include a second pressure circuit, which is supplied with pressurized fluid through a second pressure pump outlet line, and the second pressure circuit is connected to the first pressure circuit by the pressure control hydraulic line. The second pressure circuit may be a lower pressure than the first pressure circuit. The first pressure relief valve in the pressure control hydraulic line is arranged to feed an excess hydraulic pressure from the first pressure circuit to the second pressure circuit and / or to feed the second pressure circuit .

The first pressure circuit, which has a higher pressure than the second pressure circuit, can be regarded as the operating circuit. The drain valve provides safety redundancy by draining the first pressure circuit in the case of a desired depressurization of the first pressure circuit, for example due to mechanical, electronic or electrical components of the component upon which the hydraulic system relies.

At least one first pressure regulator may be arranged in the second pressure circuit, i. E. The first and second pilot pressures are diverged from the second pressure circuit.

The hydraulic system may be arranged such that the first pressure relief valve and the drain valve are sequentially actuated by the first pressure regulator. The first pressure relief valve is regulated by a first pressure regulator, which is arranged to increase the pressure from the first pressure circuit as the pilot pressure increases. The first pressure regulator can be controlled by the current, and higher currents can cause higher pilot pressures.

When the hydraulic system is started, the drain valve is closed by the first pilot pressure in the first pilot pressure line connected to the drain valve. Next, the first pressure regulator will regulate the pressure in the first pressure circuit by controlling the drain valve. Thus, using a single first pressure regulator that actuates both the drain valve and the first pressure relief valve, the drain valve can be sequentially closed as the pilot pressure increases, and then the pressure in the first pressure circuit is regulated . The pressure in the first pressure circuit may increase as the pilot pressure increases, which is regulated by the current provided to the first pressure regulator. A higher current may result in a higher pilot pressure output from the first pressure regulator. Further, the use of a single pressure regulator to actuate and / or control each of the first pressure relief valve and the drain valve may reduce the total cost of the hydraulic system, and the drain valve may add a safety margin to the clutch operating system of the hydraulic system do.

Optionally, the second pressure circuit is connected to a second pressure circuit, for example, to any other drain means such as a fluid container or to an inlet of at least one pressure pump, And a pressure relief valve.

Optionally, the at least one first pressure regulator is a normally-closed (NC) solenoid valve, and in operation the solenoid valve is operable to feed the first and second pilot pressures to the first and second pilot pressure lines Open; And in a non-operating state, the solenoid valve is closed to release the first and second pilot pressures of the first and second pilot pressure lines.

For example, when a malfunction causes the first pressure regulator to lose power, the pilot pressure will be lost and the drain valve will open. In this case, the first pressure circuit will be depressurized and will not ensure torque transmission through the transmission.

For example, after an unexpected pressure rise is detected in the first pressure circuit of the hydraulic system due to a malfunction and the NC solenoid valve is powered off, the NC solenoid valve is switched from the operating state, 2 pilot pressure line, wherein the valve is closed and the pilot pressure at the first and second pilot pressure lines is set to a predetermined value, which is required for operation of the drain valve and the first pressure relief valve It drops below the set value. As a result, the NO drain valve will open and drain excess pressure from the first pressure circuit.

In principle, the drain valve may be arranged in the hydraulic system as an NC drain valve operated by an NO solenoid valve. A normally low NL (NC) solenoid valve for providing pilot pressure to the NO drain valve, or alternatively a normally high NH (NL) solenoid valve for providing the pilot pressure to the NC drain valve. NO) solenoid valve (Normally High NH (NO) solenoid valve) improves safety because, for example, if power fails, passive fail safe is provided.

The at least one pump can supply a pressurized fluid to the first pressure circuit and the second pressure circuit, respectively. Since the drain valve is the NO direction valve, the first pressure circuit will be drained first. The first pressure regulator in the second pressure circuit will supply the first pilot pressure and the second pilot pressure to the drain valve and the first pressure relief valve, respectively. The first pressure regulator first switches the drain valve sequentially from the open state to the closed state by means of the second pilot pressure in the second pilot pressure line connected to the drain valve, The first pressure relief valve will be controlled by means of the first pilot pressure at the first pressure relief valve.

Optionally, the at least one first pressure regulator is a normally-open (NO) solenoid valve, wherein, in the actuated state, the solenoid valve is closed to release the first and second pilot pressures of the first and second pilot pressure lines And wherein, in the non-operating state, the solenoid valve opens to feed the first and second pilot pressures to the first and second pilot pressure lines. Preferably, the NO pressure regulator is arranged in association with the NC drain valve. In this way, for example, in the case of a detrimental pressure rise in at least one of the clutch and / or brake actuation lines, the NO pressure regulator may be connected to the NC drain valve, which may be drained through the drain valve, A sufficient pilot pressure to switch from the closed state to the open state can be provided to the NC drain valve.

Optionally, at least one linear solenoid valve is arranged between the first pressure circuit and each of the brake actuation lines or the clutch actuation line. The two operating lines are linked to the multi-friction transmission.

Optionally, the drain valve releases to a pressure reservoir comprising a connection to the inlet of the pump.

Optionally, the hydraulic system comprises at least two hydraulic lines for cooling at least two wet friction elements, such as a clutch and a brake, a cooler arranged in a second pressure circuit, And a dual cooling system including a brake cooling line.

At least two wet friction elements are included in the wet friction transmission. The friction elements may be clutches and / or brakes and may require cooling when extinguishing power, for example, when transmitting an increasing torque as a result of increasing hydraulic operating pressure. The cooling system plays an important role in the efficiency of the transmission. Therefore, it is important to provide an efficient cooling strategy to increase the overall efficiency of the transmission. The efficiency of the cooling system is related to the flow rate in the cooling circuit. In the case of DCT, since the mechanical power is not equally distributed to the two clutches, two cooling circuits are provided. Clutches that dissipate more power than other clutches will generally require more cooling. Thus, cooling is preferably independently controlled to provide cooling proportional to the power dissipation of the friction element. Also, if mechanical losses are too high, gear synchronization can be prevented. In this situation, cooling is adjustable so that it can be turned off at least temporarily to enable gear change. Excessive flooding of clutch assemblies with cooling fluid, which results in clutch drag, can be avoided, resulting in higher fuel efficiencies.

Optionally, the clutch cooling line and the brake cooling line each include at least one normally-closed (NC) cooling valve.

Optionally, at least one NC cooling valve in each of the clutch cooling line and the brake cooling line is actuated by a second pressure regulator and a third pressure regulator, which are arranged in a NL (Normally Low)) solenoid valves.

The dual cooling system provides individual clutch cooling, where each clutch is cooled by a dual cooling circuit, the two being regulated by a pressure regulator, i.e., a second pressure regulator and a third pressure regulator. A hydraulic system with separate cooling for independent clutches has the advantage that it is only applied where cooling is required. Without independent or separate cooling of the individual clutches, more oil flow would be required of the cooling circuit to achieve the same cooling effect per friction element, which would require a larger pump and more fuel consumption. Thus, dual cooling systems can increase the efficiency of the hydraulic system.

In addition, the dual cooling system can alone cool one clutch that dissipates more power, thereby reducing drag losses of the open clutch, which causes a reduction in fuel consumption.

In addition, by reducing the drag torque of the synchronizer, it is possible to preselect gears in a specific shaft when interrupting the cooling of the clutch without interrupting the cooling in the other clutches.

Since the actual cooling flows are regulated, the minimum flow can be selected to minimize drag losses and consequently fuel consumption.

Also, in a fail situation, cooling of the clutch and brake may be interrupted. In this situation, the absence of cooling can be dangerous to the components and / or reduce the lifetime of the components. However, this arrangement provides additional safety aspects. Under certain circumstances, the vehicle may unexpectedly set off due to losses due to cooling. This safety crisis can be avoided by the arrangement of NC cooling valves. Thus, the second pressure regulator and the third pressure regulator are arranged as NL solenoid valves to ensure a minimum drag torque on the friction elements in the event of an electrical error, thereby avoiding unintentional drive away due to this drag torque.

Optionally, the hydraulic system further comprises at least one lube line branching at said second pressure circuit for lubrication of said wet multi-friction transmission.

Optionally, the at least one pump arranged to provide pressure in the first pressure circuit and the second pressure circuit is a dual port pump.

The at least one pump may be arranged as a dual port vane pump having a first pressure and a second pressure port feeding a first pressure circuit and a second pressure circuit respectively, The output pressure at the second pressure port is higher than the output pressure at the second pressure port. The use of such dual port vane pumps does not require the use of multiple pumps in hydraulic systems. The pump may also be arranged as a regulating pump to provide a variable pressure fluid flow.

Optionally, the multiple friction transmission is a dual clutch transmission.

The hydraulic system according to the present invention may be used to operate, lubricate and / or cool a wet friction transmission.

While the first pressure circuit provides the actuation of the friction elements (clutch and / or brake) of the multiple friction transmission, the second pressure circuit, preferably having a lower pressure than the first pressure circuit, May be used for lubrication and / or cooling of the elements.

Another aspect of the present invention is to provide a hydraulic system for a multiple friction transmission including a cooling system that enables a cooling strategy that provides better control over the cooling fluid while maintaining a low cost.

Significant increases in fuel economy and vehicle performance can be achieved by the hydraulic system according to the invention.

In the present disclosure, the illustrated embodiments include one clutch and one brake, but other combinations of friction elements are possible. For example, two clutches (or two brakes or one clutch and one brake) may be applied. In other embodiments, any combination of clutches or brakes may be arranged, such as one clutch, three clutches, four clutches, and so on.

The present invention also relates to a method for controlling pressure in a hydraulic system according to the invention, comprising: supplying a pressurized fluid to the first pressure circuit using a pump; Closing the normally open drain valve by a first pilot pressure from the first pressure regulator; Adjusting the pressure in the first pressure circuit by the first pressure relief valve by a second pilot pressure from the first pressure regulator; Here, at the event of the harmful hydraulic pressure rise in the first pressure circuit, at least the second pilot pressure is lowered by the at least one first pressure regulator to switch the NO drain valve from the closed operating state to the open non- At least partially discharging the hydraulic pressure from the first pressure circuit through the line. In this manner, extra passive fail safe of the hydraulic system can be obtained.

More advantageous embodiments are indicated in the dependent claims.

The invention will be further described on the basis of exemplary embodiments shown in the drawings. Exemplary embodiments are given by way of non-limiting example. It should be noted that the figures are schematic representations of embodiments of the present invention given as non-limiting examples only.
In the drawing:
1 shows a schematic diagram of an embodiment of a hydraulic system according to the invention.
Figure 2 shows a schematic diagram of another embodiment of a hydraulic system according to the invention.
FIG. 3 shows a graph showing pressure characteristics of the exemplary embodiment shown in FIG.
FIG. 4 shows a graph representing the pressure characteristics of the exemplary embodiment shown in FIG.
Figure 5 shows a schematic diagram of another embodiment of a hydraulic system according to the invention, including a second pressure circuit.
Figure 6 shows a schematic diagram of another embodiment of a hydraulic system according to the present invention, including a second pressure circuit and a dual cooling system.
Figure 7 shows a schematic diagram of another embodiment of a hydraulic system, including a dual cooling system including a shuttle valve.

A schematic diagram of an embodiment of a hydraulic system 1 for a multiple friction transmission comprising at least two friction elements, according to the present invention, is shown in FIG. This exemplary embodiment is illustrated for a multi-friction transmission comprising two friction elements, a clutch element and a brake element. The hydraulic system 1 comprises a pressure pump 2 for supplying pressurized fluid to a first pressure circuit 3 via a first pressure pump outlet line 4, ). The hydraulic system 1 further comprises a first pressure relief valve 5 which is connected to a pressure controlled hydraulic line branching at the first pressure pump outlet line 4 6). The first pressure relief valve 5 is adjustable by means of a first pilot pressure through a first pilot pressure line 7. The hydraulic system 1 further comprises a drain valve 8 which is arranged in a pressure drain hydraulic line 9 which branches off from the first pressure pump outlet line 4 , Which is different from the pressure control hydraulic line (6). The drain valve 8 is connected by a means of a second pilot pressure through a second pilot pressure line 10 to a NO directional valve which is switchable between an open state and a closed state, (NO directional valve). The hydraulic system 1 includes a first pressure regulator 11 for actuating the first pressure relief valve 5 and the drain valve 8 by means of a first pilot pressure and a second pilot pressure, ). The second pilot pressure line 10 is, for example, in fluid communication branched from the first pilot pressure line 7 (the second pilot pressure line 10 is in fluid communication, for example, branched off from the first pilot pressure line 7). The first pressure regulator 11 switches the NO drain valve 8 from the closed operating state to the open inoperative state by means of the second pilot pressure at the event of the hydraulic pressure rise which is harmful to the first pressure circuit And at least partially discharges the hydraulic pressure from the first pressure circuit 3 through the drain line 12. [ The hydraulic system 1 may further comprise hydraulic lines for operating the wet friction elements of the multi-friction transmission. In the embodiment of Figure 1, the clutch elements and the brake elements, i.e. the two hydraulic lines for the actuation of the clutch actuating line 13 and the brake actuating line 14, are arranged in a direct acting solenoid valve ) 15, 16, respectively. In some cases, during a sudden pressure rise in one or more hydraulic operating lines (13, 14) connected to, for example, the clutch and / or brake and diverged from the first pressure circuit (3) The valve 5 may not be suitable for proper draining of the pressure in the first pressure circuit 3 while the drain valve 8 drains the pressurized fluid from the first pressure circuit 3 It may be suitable for releasing pressure and handling sudden pressure rises. The pressurized fluid may be drained through the drain valve 8, for example to the reservoir, the inlet of the pump, the inlet of another pump and / or other pressure circuits.

By arranging the NO drain valve 8 in the hydraulic system 1, a passive fail-safe can be obtained, wherein the pilot pressure and / or current is not required in the hydraulic system 1, The first pressure circuit 3 may be drained to reduce the hydraulic pressure in at least one of the clutches and / or operating lines 13, 14, in the case of a detrimental pressure rise in the first and second valves 13, However, it is also possible to arrange the drain valve in the hydraulic system 1 as an NC directional valve. The hydraulic system comprising the NC drain valve will require a second pilot pressure, which is provided to the drain valve by the first pressure regulator through the second pilot pressure line 10, for example to the clutch and / The drain valve is opened to drain the first pressure circuit (3) in the case of a pressure rise which is detrimental to at least one of the first and the second pressure circuits (13, 14).

A schematic diagram of another exemplary embodiment of a hydraulic system 1 according to the present invention is shown in Fig. The drain valve 8a is arranged as a switchable NC directional valve 8a between an open state and a closed state by means of a second pilot pressure provided to the drain valve 8a through a second pilot pressure line 10 . The first pressure regulator 11a is arranged as an NO solenoid valve. The NC drain valve 8a can be opened by the second pilot pressure provided through the second pilot pressure line 10. [ At the event of a detrimental hydraulic pressure rise in one or more hydraulic operating lines 13,14 the hydraulic system 1 drains the first pressure circuit 3 through the drain valve 8a to the drain line 12 The pressure in the operating lines 13, 14 can be reduced. In this case, the current supplied to the solenoid will be lowered so that the NO first pressure regulator 11a will be switched from the operative closed state to the inoperative open state. The pilot pressure provided to the first pilot pressure line 7 and the second pilot pressure line 10 by the first pressure regulator 11a regulates the first pressure relief valve 5a and the NC pressure of the NC drain valve 8a Will be high enough to switch from the non-actuated closed state to the actuated open state. Thus, the drain valve 8a will be opened by the second pilot pressure to drain the first pressure circuit 3.

The outline of the sequential function of the first pressure relief valve 5 and the drain valve 8 can be illustrated by using the graph showing the line pressure P in the function of the pilot pressure P _pilot . The line pressure P is the hydraulic pressure in the first pressure circuit. The first pressure relief valve (5) and the drain valve (8) are provided with a pilot pressure through a first pilot pressure line (7) and a second pilot pressure line (10), respectively. Fig. 3 shows the relationship between the line pressure P and the pilot pressure P _pilot for the embodiment of the hydraulic system 1 shown in Fig. The pilot pressure P _pilot from the first pressure regulator 11, which may be proportional to the current provided to the solenoid of the first pressure regulator 11, can be increased. In addition, an increase in the pilot pressure P _pilot by the pressure regulator 11 will increase the first pilot pressure and the second pilot pressure in the first pilot pressure line 7 and the second pilot pressure line 10, respectively. Initially, when increasing the pilot pressure P _pilot , the pressure is too low to close the NO drain valve 8 in the normally open condition. However, as the pilot pressure gradually increases (points a to b), the pilot pressure P _pilot will reach a value (point b) sufficient to close the NO drain valve 8 from the open state to the closed state. When the drain valve 8 is closed, the line pressure P can be increased by adjusting the pressure to the relief valve 5 (points c to d) until the desired line pressure (point d) is obtained. Therefore, NO drain valve 8 is first closed by the pilot pressure P _pilot in the pilot pressure line 10, and then the line pressure P is a relief valve (5 into the pilot pressure P _pilot in the pilot pressure line (7) ) Until the desired pressure value is obtained.

4 shows the relationship between the pilot pressure and the line pressure from the pressure regulator 11 of the exemplary embodiment shown in Fig. In this embodiment, the NC drain valve is arranged in the hydraulic system 1. As shown in Fig. 4, the line pressure P is a function of the pilot pressure P _pilot provided by the first pressure regulator 11. The line pressure P is gradually reduced (points a to b) by the first pressure relief valve 5a until the pilot pressure P _pilot reaches a predetermined value (point b). When the pilot pressure is further increased, the second pilot pressure in the second pilot pressure line 10 reaches a value (point c) sufficient to switch the NC drain valve 8a from the non-operation closed state to the operation open state , The first pressure circuit 3 can be drained through the drain valve.

Fig. 5 shows another advantageous embodiment of the hydraulic system 1 according to the invention, wherein the hydraulic system 1 further comprises a second pressure circuit 17. Fig. The pressure in the first pressure circuit 3 and the pressure in the second pressure circuit 17 is controlled by two outlets connected to the outlet lines 4 and 21 and a suction inlet 19 is provided by a dual port pump 18 which includes an injection inlet 19 and an injection inlet 20. The second pressure circuit (17) is supplied with the pressurized fluid through the second pressure pump outlet line (21). The second pressure circuit 17 is also connected to the first pressure circuit 3 by way of the pressure control hydraulic line 6 via the first pressure relief valve 5. The second pressure circuit 17 is maintained at a pressure lower than that of the first pressure circuit 3. For example, a dual port pump may be a vane pump, possibly asymmetric. The first pressure relief valve 5 in the pressure control hydraulic line 6 is arranged to drain the excess hydraulic pressure from the first pressure circuit 3 to the second pressure circuit 17 and / 17). Preferably, the first pressure regulator (11) is arranged in the second pressure circuit (17). In addition, the first pressure relief valve 5 and the drain valve 8 are controlled by the same first pressure regulator 11. The second pressure circuit 17 controls the pressure in the second pressure circuit 17 by discharging the second pressure circuit 17 to the injection inlet 20 of any other drain circuit or dual port pump 18 And a second pressure relief valve (22). The first pressure regulator 11 is a normally-closed (NC) solenoid valve which is open to feed the first and second pilot pressures into the first and second pilot pressure lines 7, 10, respectively, , And to release each of the first and second pilot pressures of the first and second pilot pressure lines (7, 10) in the non-operating state. The first and second pilot pressures are diverged from the second pressure circuit. The second pilot pressure line 10 is diverged from the first pilot pressure line 7, for example in fluid communication. At least two hydraulic friction elements, namely two hydraulic lines for the actuation of the clutch actuating line 13 and the brake actuating line 14, are connected to the first pressure circuit 3. The linear solenoid valves 15 and 16 are arranged between the first pressure circuit 3 and the brake operation line 13 and the clutch operation line 14, respectively. The drain valve 8 releases pressure to the pressure reservoir 23, which is connected to the suction inlet 19 of the dual port pump 18.

Another preferred exemplary embodiment of the hydraulic system 1 according to the present invention is shown in Fig. The hydraulic system 1 of this embodiment is used in a multi-friction transmission of a vehicle comprising wet friction elements, namely a clutch element and a brake element. The multi-friction transmission in this embodiment may be DCT. The hydraulic system 1 further comprises a first pressure circuit 3 fed with pressurized fluid through a first pressure pump outlet line 4 of the dual port pump 18. [

The first pressure relief valve 5, which is adjustable by means of the first pilot pressure through the first pilot pressure line 7, is connected to the pressure control hydraulic line 6 branched from the first pressure pump outlet line 4 .

The drain valve 8 is arranged in the pressure drain hydraulic line 9 branched at the first pressure pump outlet line 4 and the drain hydraulic line 9 is different from the pressure control hydraulic line 6. The drain valve 8 is a normally-open (NO) directional valve switchable between an open state and a closed state by means of a second pilot pressure through a second pilot pressure line. The drain valve 8 releases the pressure to the pressure reservoir 23, including the connection to the suction inlet 19 of the dual port pump 18. The filter is further arranged in a sump 26 which is arranged between the suction inlet 19 of the dual port pump 18 and the pressure reservoir 23 so that the fluid of the hydraulic system 1, Is sucked through an emerged suction filter emptied from the sump 26. The drain valve 8 is spring biased to the open position and the drain valve 8 is fully opened to communicate with the reservoir 23. The second pilot pressure from the second pilot pressure line 10 acts on the bias spring so that when a sufficient pilot pressure through the second pilot pressure line 10 operates on the drain valve 8, The pilot pressure in the second pilot pressure line 10 will overcome the biasing force and will change the state of the drain valve 8 from the open state to the closed state and in the closed state the first pressure circuit 3 Is not drained to the reservoir 23 through the drain valve 8. [0050]

The hydraulic system 1 further comprises a first pressure regulator 11 for actuating the first pressure relief valve 5 and the drain valve 8 by means of a first pilot pressure and a second pilot pressure, respectively. The first pressure regulator 11 is arranged to switch the NO drain valve 8 from the closed operating state to the open non-operating state by the means of the second pilot pressure at the event of the hydraulic pressure rise which is harmful to the first pressure circuit, And at least partially discharges the hydraulic pressure from the first pressure circuit (3) through the drain line (9). Thus, the hydraulic system 1 includes redundant passive fail safes, which can improve safety. The first pressure regulator 11 arranged in the second pressure circuit 3 regulates the pressure in the first pressure circuit 3 by controlling the first pressure relief valve 5 and the drain valve 8. The first pressure regulator 11 is a normally-closed (NC) solenoid valve 11. In the operating state, the solenoid valve 11 is opened to feed the first and second pilot pressures to the first and second pilot pressure lines 7, 10, respectively. In the non-operating state, the solenoid valve 11 is closed to release the first and second pilot pressures of the first and second pilot pressure lines 7, 10, respectively. The first and second pilot pressures are diverged from the second pressure circuit. The second pilot pressure line 10 is in fluid communication, i. E., Branched from the first pilot pressure line 7. The NC solenoid valve 11 further includes a biasing element (spring) biasing the valve to the closed position, and the second pressure circuit 17 includes a first pilot pressure line and a second pilot pressure line 7, 10). When the solenoid of the first pressure regulator 11 is energized, the valve will be electromechanically activated to open, and the second pressure circuit 17 will open the first pilot pressure line and the second pilot pressure line 7, 10) can be fed and communicated. As a result, when the solenoid is energized and the valve member of the first pressure regulator is opened, the pilot pressure in the second pilot pressure line 10 and / or the first pilot pressure line 7 is lower than the pilot pressure in the drain valve 8, And the first pressure relief valve 5, respectively. When the current used to actuate the solenoid of the first pressure regulator 11 is too low, for example in the case of an electrical, electronic and / or control system malfunction, the first pressure regulator 11 is in an inactivated closed state I will go back. In this deactivated closed state, the first pressure regulator 11 is arranged to sufficiently depressurize the first pilot pressure line 7 and the second pilot pressure line 10. Alternatively, the damper 41 may be arranged in the hydraulic line branched from the first pilot pressure line 7 or the second pilot pressure line 10. [ The damper 41 is arranged to damp pressure oscillations to increase the pressure stability. In this way, adverse pressure peaks and / or pressure fluctuations in the pilot pressure lines 7, 10 are at least partially smoothed out by the dampers 41 ).

The first pressure circuit 3 provides the hydraulic action of the friction elements of the multi-friction transmission, i.e., the clutch element and the brake element. The hydraulic system 1 further comprises two hydraulic lines connected to the first pressure circuit 3 for the respective operation of the clutch element and the brake elements, namely the clutch operating line 13 and the brake operating line 14, . The linear solenoid valves 15 and 16 are arranged between the first pressure circuit 3 and each of the brake operation lines 14 and the clutch operation line 13 to control the pressure in the lines 13 and 14 do. The clutch operating line 13 and the brake operating line 14 are each linked to a multi-friction transmission. The pressures of the clutch operating line 13 and the brake operating line 14 can be measured with the pressure sensors 24 and 25. Each of the actuation lines 13,14 may comprise pressure sensors 24,25. The pressure measured by the pressure sensor can be used by a hydraulic control system for controlling the hydraulic system 1. [ Preferably, the damper 27 is arranged in the clutch operating line 13 and the brake operating line 14 to damp the pressure and increase the pressure stability. For example, the back pressure peaks and / or pressure fluctuations may be at least partially removed by dampers 27 in the actuation lines 13,14. The linear solenoid valves 15 and 16 in the wet friction element operating lines 13 and 14 have three ports and two finite positions, namely a first open position and a second closed position It is a normally closed directional control valve. The solenoid valves can be electromechanically actuated by current. The linear solenoid valves 15 and 16 are spring biased to the first position, and the valve is closed. The direct-acting solenoid valves 15, 16 will be switched to the second or open position when the solenoid is energized.

The hydraulic system (1) further comprises a second pressure circuit (17) through which the pressurized fluid is supplied via the second pressure pump outlet line (21). The hydraulic system 1 is configured such that the second pressure circuit 17 is at a lower pressure than the first pressure circuit 3. [ The second pressure circuit 17 is connected to the first pressure circuit 3 by way of the pressure control hydraulic line 6 through the first pressure relief valve 5. The first pressure relief valve 5 in the pressure control hydraulic line 6 is connected to the second pressure circuit 17 to drain the excess hydraulic pressure from the first pressure circuit 3 and / .

The pressure of each of the first pressure circuit 3 and the second pressure circuit 17 is controlled by a first pressure port connected to the first pressure pump outlet line 4 and a second pressure port connected to the second pressure pump outlet line 21, Port vane pump 18, which includes the outlet line 4, 21, which feeds the first pressure circuit 3 and the second pressure circuit 17, respectively. The output pressure at the first pressure port is higher than the output pressure at the second pressure port. The use of such a dual port vane pump 18 may make the use of multiple independent pumps in the hydraulic system 1 unnecessary.

The second pressure circuit (17) further includes a second pressure relief valve (22) for controlling the second pressure circuit pressure (17). The second pressure relief valve 22 connects the second pressure circuit 17 with the injection inlet 20 of the dual port pump 18. The second pressure relief valve 22 includes a pressure biasing element, such as a spring, which is configured such that the pressure of the communicated fluid at the inlet of the valve can be limited in view of the pressure at the inlet. The second pressure relief valve 22 also includes a sensing port communicating with a hydraulic line connected to the inlet of the valve via an orifice.

The first pressure relief valve (5) is arranged as a pressure regulating valve between the first pressure circuit (3) and the second pressure circuit (17). The first pressure relief valve (5) includes an inlet connected to the first pressure circuit (3) and an outlet connected to the second pressure circuit (17). When the hydraulic system 1 of the multi-friction transmission operates, the pressure of the pressurized fluid in the second pressure circuit 17 is lower than the pressure in the first pressure circuit 3. The first pressure relief valve 5 also includes a sensing port communicated via an orifice with the hydraulic control line 6 in the first pressure circuit 3. In addition, the first pressure relief valve 5 includes a pressure setting spring, which ensures that the pressure of the pressurized fluid (e.g., oil) at the inlet of the first pressure relief valve 5 is at a desired and / Lt; / RTI >

The hydraulic system 1 includes a cooler 29 arranged in a second pressure circuit 17 and two hydraulic lines for cooling the clutch element and brake elements, namely the clutch cooling line 30 and the brake cooling line 31 And a dual cooling system 28 that includes a plurality of heat exchangers. Each of the clutch cooling line 30 and the brake cooling line 31 includes normally-closed (NC) cooling valves 32 and 33 and each of the cooling valves 32 and 33 is arranged in a second pressure circuit 17 NL solenoid valves 34 and 35, respectively. The cooling flows in the clutch cooling line 30 and the brake cooling line 31 are independently adjusted by the cooling valves 32 and 33, respectively. The cooling valves 32 and 33 include a biasing member (spring) that acts on the valve member of the cooling valve and biases it to a normally closed position. The cooling valve 32 in the clutch cooling line 30 has a bypass line for ensuring a constant minimum flow. The cooling valves 32 and 33 have feedback from the controlled pressure and are operated by the second pressure regulator 34 and the third pressure regulator 35, respectively. The second pressure regulator 34 includes a port connected to a third pilot pressure line 36 communicating with the cooling valve 32 arranged in the clutch cooling line 30. Similarly, the third pressure regulator 35 includes a port connected to a fourth pilot pressure line 37 communicating with a cooling valve 33 arranged in the brake cooling line 31. The pilot pressure received from the second pressure regulator 34 and the third pressure regulator 35 by the cooling valves 32 and 33 respectively is applied to the biasing force of the biasing element of the cooling valves 32 and 33 It works against. When the pilot pressure is sufficiently high, the cooling valves 32, 33 open to selectively and independently provide a flow of cooling fluid to the wet friction elements (clutch element, brake element). In this way, the correct cooling flow can be applied by controlling the pressure drop on the cooling valves 32, 33. An external oil-to-water cooler 29, with a parallel bypass valve 38, for limiting the pressure drop to the cooler 29, (17). The cooling and lubrication fluid may flow through the oil-water cooler 29 to achieve the required heat-exchange required in the hydraulic system 1. The temperature sensor is arranged in the vicinity of the cooler or at the sump, or at two positions, in order to obtain an indication of the thermal behavior of the hydraulic system or to obtain a temperature measurement, which, among other aspects, comprises wet friction elements, It depends on the energy dissipation in the element. Thus, the two, the second pressure regulator 34 and the third pressure regulator 35 arranged in the second pressure circuit 17 regulate the cooling of the friction elements of the multiple friction transmission. The damper may be arranged to damp the regulated pressure.

Each of the NC solenoid valves of the second pressure regulator 34 and the third pressure regulator 35 includes a biasing element (spring) biasing the valve to a closed position and the second pressure circuit 17 comprises a clutch cooling pilot Pressure line 36 and the brake cooling pilot pressure line 37 in direct fluid communication. When the solenoid of the pressure regulators 34 and 35 is energized, the valve will be electromechanically activated to open so that the second pressure circuit 17 can feed and communicate the pilot pressure lines 36 and 37 connected thereto have. As a result, when the solenoid is energized and the valve members of the pressure regulators 34, 35 are opened, the pilot pressure at the pilot pressure lines 36, 37 connected with the pressure regulators 34, , And 33, respectively. When the current to the solenoid is too low, for example in the case of electrical, electronic and / or control system malfunctions, the pressure regulators 34 and 35 will return to the non-operating closed state. In this non-actuated closed state, the pressure regulators 34, 35 are arranged to sufficiently depressurize the pilot pressure lines 36, 37 connected thereto.

The hydraulic system further includes two lube lines (39, 40) diverging from the second pressure circuit for lubrication of the wet multi-friction transmission.

Figure 7 shows a schematic diagram of another embodiment of the hydraulic system 1 according to the invention. The hydraulic line connected to the output of the drain valve 8 is connected to the injection inlet 20 of the dual port pump 18. The first pressure pump outlet line (4) of the dual port pump (18) is connected to the first pressure circuit (3) to feed the pressurized fluid to the circuit (3). The second pressure pump outlet line 21 of the dual port pump 18 is also connected to the second pressure circuit 17 to feed the pressurized fluid to the circuit 17. The first pressure circuit 3 is connected to the second pressure circuit 17 via the first pressure relief valve 5 which causes excessive oil to flow from the first pressure circuit 3 to the second pressure circuit 17 Feed and / or drain. The first pressure relief valve (5) is controlled by the first pressure regulator (11). The first pressure relief valve 5 is thus arranged between the high pressure outlet and the low pressure outlet of the dual port pump 18 connected to the first pressure pump outlet line 4 and the second pressure pump outlet line 21, do. The outlet of the second pressure relief valve (22) is connected to the injection inlet (20) of the dual port pump (18). Thus, the hydraulic line connected to the outlet of the second pressure relief valve (22) communicates with the hydraulic line connected to the outlet of the drain valve (8). The drain valve 8 and the first pressure relief valve 5 are controlled such that the pilot pressure provided by the first pressure regulator 11 through the first pilot pressure line 7 and the second pilot pressure line 10 is changed , It is operated sequentially. For example, in the case of mechanical, electrical, electronic or other kinds of malfunctions which cause a pressure rise in the first pressure circuit 3, the drain valve 8 is connected to the first pressure circuit 3 via a dual port pump 18 will be added to the injection inlet 20 to add a safety margin. The first pressure circuit 3 is used for the actuation of the friction elements (clutch element, brake element) through the clutch operating line 13 and the brake operating line 14.

The cooling system 28 of the embodiment shown in Figure 7 includes NC solenoid valves 42 and 43 arranged as cooling valves 42 and 43 of the clutch cooling line 30 and the brake cooling line 31, do. The cooling valves 42 and 43 can be directly controlled by the solenoids arranged therein. The third and fourth pressure regulators in the second pressure circuit 17 are arranged for the operation of the cooling valves 42 and 43 in each of the clutch cooling line 30 and the brake cooling line 31 no need. The cooling valves 42 and 43 are used to provide a biasing element for automatically closing the valve when the solenoid is not actuated, for example if an electrical malfunction occurs due to too low a current to the solenoids for operation As an NC solenoid valve. The hydraulic system 1 further comprises a shuttle valve 44 arranged in the hydraulic line connecting the clutch cooling line 30 and the brake cooling line 31. [ The shuttle valve 44 is arranged to select the highest line pressure between the clutch cooling line 30 and the brake cooling line 31. Feedback is provided to the shuttle valve 44 via a feedback line 45 communicating with the second pressure relief valve 22 to maintain a substantially constant pressure drop across the cooling lines 30, 2 pressure relief valve 22, which may be useful in evaluating the cooling flow to the friction elements (clutch element, brake element) in a multi-friction transmission.

5-7 include a first pressure circuit 3 and a second pressure circuit 17, and the pressure of the pressurized fluid in the second pressure circuit 17 is controlled by the first pressure circuit < RTI ID = 0.0 > Is lower than the pressure of the pressurized fluid in the pressurizing chamber (3). For example, the pressure in the first pressure circuit 3 can generally be between 5 and 17 bar, and the pressure in the second pressure circuit 17 can generally be between 5 and 6 bar. The pressure in the first, second, third and fourth pilot pressure lines (7, 10, 36, 37) may generally be between 0 and 5 bar. The pressure in the clutch operating line 13 and the brake operating line 14 can generally be between 0 and 15 bar. The pressure at the pump inlet port and the line connected to the second pressure relief valve 22 can generally be between 0 and 1 bar. The range of the above-mentioned pressures in the hydraulic lines of the hydraulic system 1 is exemplary and should not be construed as limiting the scope of the present invention. Other configurations are possible and within the scope of the present invention.

The pressure sensors 24 and 25 are also arranged in the clutch operating line 13 and the brake operating line 14 to measure the pressure in the lines 13 and 14. Preferably, the pressure characteristics in the first pressure circuit 3 open one of the linear solenoid valves 15, 16 arranged in the clutch operating line 13 and the brake operating line 14, Can be evaluated by measuring the pressure with the pressure sensors 24, 25 in the lines 13, Similarly, the pressure first adjuster 11 may also be calibrated.

Preferably, the drain valve, the first pressure relief valve 5 and the second pressure relief valve 22 are connected to the valve 5, 22 in such a way that they affect the fluid inflow and outflow angles May be arranged to have an asymmetric cove. Other valves in the hydraulic system may have such an arrangement.

The invention is now described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made thereto without departing from the spirit of the invention. For clarity and for brevity, although the features have been described herein as part of the same or independent embodiments, other embodiments having all or part of the combinations of features described in these individual embodiments are also contemplated.

The solenoid valves 11, 15, 16, 34, 35 described above in the illustrated embodiments include solenoids, which may be controlled by a microprocessor-based electronic control device. The electronic control unit may be arranged to control the hydraulic control system 1 for electronic control of the hydraulic system 1 according to the present invention. The electronic control device is capable of detecting multiple signals as input signals from a plurality of sensors such as, for example, a ground speed signal, a wheel speed, an engine speed, an engine throttle position, a lever position, Parameters may be received. The hydraulic control system may be implemented with dedicated electronic circuits, possibly including software code portions. Further, the hydraulic control system may be embodied as software code portions stored and executed in a memory of a programmable apparatus such as, for example, a computer.

Although the present invention has been described with reference to specific embodiments relating to multi-friction transmissions, and more particularly to dual clutch transmissions (DCT), the hydraulic system according to the present invention may also be applied to other types of transmissions requiring the hydraulic system 1 And the like. The hydraulic system 1 may also be used to control fluid communication with other high pressure and / or low pressure hydraulic functions such as, for example, steering, brakes, suspensions, and the like. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope of the appended claims.

Other variations, modifications and alternatives are also possible. Accordingly, the detailed description, drawings, and illustrations should be regarded as illustrative rather than limiting. The invention is intended to cover all alternatives, modifications and variations that fall within the spirit and scope of the appended claims.

For purposes of clarity and for brevity, although features have been described herein as part of the same or separate embodiments, it is to be understood that the scope of the invention may include embodiments having all or part of some of the described features will be.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word " comprising " does not exclude the presence of other features or steps than those listed in a claim. In addition, the words 'a' and 'an' should not be construed as being limited to 'only one', but rather 'at least one' And does not exclude plurality. The mere fact that a particular method is recited in different claims does not indicate that a combination of such methods can not be used advantageously.

Claims (15)

A hydraulic system for a vehicle transmission having multiple friction elements for connecting and transmitting engine power to the wheels of a vehicle by actuation of friction elements through the hydraulic system (1)
The hydraulic system (1)
At least one pressure pump (2, 18) for supplying a pressurized fluid to the pressure circuit (3) through a first pressure pump outlet line (4), at least one pressure pump Said pressure circuit in fluid connection;
At least one first pressure regulator (11, 11a) for actuating the first pressure relief valve (5, 5a) by means of a first pilot pressure through a first pilot pressure line (7);
The first pressure relief valve (5, 5a) is arranged in a pressure control hydraulic line (6) branched at the first pressure pump outlet line (4), and the first pressure relief valve Controlled by means of said first pilot pressure to control the pressure in said pressure circuit (3);
The drain valves 8 and 8a arranged in the pressure drain line 9 branching from the first pressure pump outlet line 4 different from the pressure control hydraulic line 6 and the drain valves 8 and 8a Is a directional valve switchable between an open state and a closed state by means of a second pilot pressure through a second pilot pressure line (10), said second pilot pressure being in fluid communication with said first pilot pressure
≪ / RTI > The method according to claim 1,
The drain valve is connected to the normally-open (NO) directional valve 8
Hydraulic system. The method according to claim 1,
The drain valve is a normally-closed (NC) directional valve 8a
Hydraulic system. 4. The method according to any one of claims 1 to 3,
Further comprising a second pressure circuit (17) through which a pressurized fluid is supplied through a second pressure pump outlet line (21), said second pressure circuit (17) Is connected to the pressure circuit (3) and the first pressure relief valve (5, 5a) in the pressure control hydraulic line (6) is connected to the second pressure circuit (17) (Not shown) to drain the excess hydraulic pressure, and / or to feed the second pressure circuit 17
Hydraulic system. 5. The method of claim 4,
The at least one pressure regulator (11) is arranged in the second pressure circuit (17)
Hydraulic system. The method according to claim 4 or 5,
The second pressure circuit (17) further comprises a second pressure relief valve (22) for controlling the second pressure circuit pressure (17)
Hydraulic system. 7. The method according to any one of claims 1 to 6,
Wherein said at least one first pressure regulator 11 is a normally-closed (NC) solenoid valve 11 and, in operation, said solenoid valve 11 is connected to said first and second pilot pressure lines 7, Respectively, to feed said first and second pilot pressures; And the solenoid valve 11 is closed to release the first and second pilot pressures of the first and second pilot pressure lines 7, 10, respectively,
Hydraulic system. 8. The method of claim 7,
At least one linear solenoid valve (15, 16) is arranged between the first pressure circuit (3) and each of the clutch operating line (13) and the brake operating line (14)
Hydraulic system. 9. The method according to any one of claims 1 to 8,
The drain valve (8, 8a) releases to the pressure reservoir (23) which includes the connection to the inlet of the pump (2, 18)
Hydraulic system. 10. The method according to any one of claims 4 to 9,
The brake and clutch are formed by respective wet friction elements,
The hydraulic system comprises a dual cooling system (28) comprising a cooler (29) arranged in the second pressure circuit (17) and a second cooling system (28) through the clutch cooling line (30) and the brake cooling line Further comprising at least two hydraulic lines (30, 31) for cooling the elements
Hydraulic system. 11. The method of claim 10,
The clutch cooling line 30 and the brake cooling line 31 comprise at least one normally-closed (NC) cooling valve 32, 33, respectively,
Hydraulic system. 12. The method according to any one of claims 4 to 11,
The at least one NC cooling valve (32, 33) in each of the clutch cooling line (30) and the brake cooling line (31) is connected to an NL solenoid valve Lt; RTI ID = 0.0 >
Hydraulic system. 13. The method according to any one of claims 4 to 12,
At least one lubricating line (16) branching at said second pressure circuit (17) for lubrication of said wet multiple friction transmission
And a hydraulic system. The method according to any one of claims 4 to 13,
The at least one pump (2, 18) arranged to provide pressure in the first pressure circuit (3) and the second pressure circuit (17) is a dual port pump (18)
Hydraulic system. A method for controlling a pressure in a hydraulic system for a vehicle transmission having multiple friction elements for connecting and transmitting engine power to the wheels of the vehicle by operation of the friction elements through the hydraulic system (1) ,
Supplying a pressurized fluid to a pressure circuit (3) in fluid communication with a friction element of the transmission;
Actuating the first pressure relief valve (5, 5a) by means of a first pilot pressure through a first pilot pressure line (7); The first pressure relief valve (5, 5a) is arranged in a pressure control hydraulic line (6) which branches at the first pressure pump outlet line (4) to control the pressure in the pressure circuit (3);
Switching the drain valves (8, 8a) in the pressure drain line (9) which diverge from the first pressure pump outlet line (4) different from the pressure control hydraulic line (6) 8a) is a directional valve switchable between an open state and a closed state by means of a second pilot pressure through a second pilot pressure line (10), said second pilot pressure being in fluid communication with said first pilot pressure has exist
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